JPH1038677A - Radiation detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a radiation detector capable of avoiding scene-setting time. SOLUTION: A detector 200 contains two photoconductors 202 and 204, an operational amplifier 210 with a feedback resistance 212, a correlated double sampler 220, and a timing and bias controlling circuit 230. The photoconductors 202 and 204 can be formed of the two parts of a single resistance film of amorphous silicon. electronic bias switching and correlated double sampling attenuate low frequency noise in great amounts as mechanical chopping and correlated double sampling.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Cross Reference of Related Application]
US Provisional Application Serial Number 60 filed July 21, 2016
No./001,334.

[0002]

TECHNICAL FIELD The present invention relates to an electronic device,
In particular, it relates to devices such as radiation detectors and sensors that include such detectors.

[0003]

BACKGROUND OF THE INVENTION Infrared detection offers an important solution for night vision (imaging based on radiation from warm bodies), chemical analysis (spectral absorption) and various other fields. Infrared detectors can be single detectors or pixel arrays, cryogenic (typically liquid nitrogen temperature) or uncooled detectors, 8-12 (lm) or 3-5 (lm) or other wavelengths. Various classifications can be made, such as sensitivity and photon or heat detection mechanism. Photon detection (photoconductor,
Photodiodes and photocapacitors) work by photon absorption that creates electron-hole pairs in a small bandgap semiconductor material, and this increase in the number of electrical carriers is detected. On the other hand, heat detection works by changes in electrical resistance or capacitance due to heating of the element that absorbs infrared photons. Detectors that rely on resistance changes due to photon heating are called bolometers.

US Pat. No. 5,021,663 to Hornbeck and US Pat. No. 5,288,649 to Keenan disclose CM in the form of a single semiconductor integrated circuit for use in night vision.
Disclosed is an array of amorphous silicon bolometers suspended therefrom from an OS control and drive circuit.
In particular, FIG. 1 schematically illustrates a lens system 102, an array of bolometers 106, and circuitry for infrared imaging. FIG.
Shows a single bolometer circuit. FIG. 3 shows a part of the arrangement of the bolometer 140. Each bolometer provides a signal for one pixel of a two-dimensional image. Bolometers suspended on an integrated circuit substrate provide thermal isolation, but also create mechanical support problems. There is also a problem in the bolometer packaging in that the ambient atmosphere causes thermal coupling between the bolometer and the detector lead wires in close proximity to the bolometer, resulting in crosstalk.

[0005] In FIG 2, R _B represents a temperature variable resistor, R _L is a temperature-independent load resistance, and shows the R _B and R bias voltage to the applied + V to a series circuit of _L for a single bolometer I have. Temperature variation of R _B due to changes in the infrared radiation intensity input when obtaining the night vision is typically 1
It is below Kelvin degree. Resistance variation with temperature variation of R _B is generated, thereby inducing a voltage variation across the load resistor R _L, the voltage to drive the output amplifier. Typically, low frequency noise of the bolometer exceed Johnson noise (white noise amplitude proportional to the resistance) regarding R _B, and increases the bias voltage applied between R _B. Furthermore, the magnitude of the signal detected by R _B -R _L series is proportional to the bias voltage. Also, a bias sufficient to produce a measurable signal sometimes produces unacceptable levels of low frequency noise.

[0006] Infrared photoconductor detectors also typically have excessive low frequency noise. A common approach to solving this low frequency noise problem is to chop the input radiation (periodic mechanical shielding), measure the output of both the illuminated and dark states, and then derive the dark state output from the illuminated state output. Subtracting to give a net output (modified double sampling). Such chopping significantly attenuates the effects of low frequency noise and improves the signal-to-noise ratio of the detector.

[0007]

The chopping input method, however, involves the high cost and low reliability of mechanical systems. In addition, heat detectors such as bolometers require significant scene setup time to accurately represent this signal level. For example, for a bolometer, it is not unusual to require a signal interval of 30 milliseconds to obtain reliable signal reproduction. Thus, there is a maximum scene chopping frequency. However, the effectiveness of the modified double sampling depends on the scene chopping frequency being greater than the "1 / f knee" frequency in the noise intensity spectrum of the detector. Thus, mechanical chopping may be because the maximum scene chopping frequency, which depends on the scene setting time, may be less than the 1 / f knee frequency.
It is not always a valid mechanism.

[0008] Bolometers and photoconductors also
Detects visible and near ultraviolet light and is not limited to applications for infrared, for example, applications to colorimeters are just to different wavelengths.

No. 5,163,332 to Wong and US Pat. No. 4,709,150 to Blow et al. Disclose the use of infrared detectors to detect atmospheric CO ₂ or other gases by measuring the absorption of spectral lines by the gas. Is shown.

[0010]

SUMMARY OF THE INVENTION The present invention provides a multi-wavelength pixel array, electronic chopping and self-calibration, internal shading in a multiple detector vacuum package, pixel redundancy, common support and hidden support. Provided is a bolometer with a sealed bolometer, a tilted leg support for a suspended bolometer, and a gas sensor having an infrared source and a bolometer detector for spectral analysis.

The features of the present invention are as follows. Multiple detectors with different filters can detect multiple bands,
Therefore, it can be an integrated sensor for multiple gases.
A sealed redundant bolometer increases sensitivity, and the tilted leg support provides mechanical strength to the suspended bolometer. Internal shadows with widely spaced detectors limit crosstalk in compact packages. Electronic chopping has the advantage that mechanical chopping can be eliminated and the scene setting time, which is a frequency limitation at the chopping frequency, can be avoided.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred Embodiment of a Two-Component Pixel FIGS. 4 and 5 show a detector of a preferred embodiment of a two-component resistive element, which is indicated generally by the reference numeral 200. 202, 204, an operational amplifier 210 with a feedback resistor 212, a correlated double sampler 220, and a timing and bias control circuit 230. Photoconductors 202 and 20
4 can be formed from two portions of the amorphous silicon single resistance film 306, as shown in the plan view of FIG. 6 and the vertical sectional view of FIG. The metal contacts 310 divide the film 306 into two equal parts with contacts 312, 314 parallel to the metal contacts 310 at the end of the film 306. The metal contacts are formed from another metal such as aluminum or nickel.
The contacts 310, 312 and the portion of the membrane 306 therebetween form the photoconductor 202, and the contacts 310, 312
14 and the portion of membrane 306 therebetween form photoconductor 204. The membrane 306 is 50 (lm) × 50 (l
m) is 200 (nm) thick, and the silicon substrate 30
2 on the silicon dioxide (oxide) layer 304. Photoconductors 202 and 204 are both about 20 megaohms in the dark and 5 × 10 ⁻⁴ w at 0.3-1.2 lm wavelength.
It is 1% lower at a photons flux of atts / cm ² . The detector 200 may be a single pixel in a picture element array for picture detection or a single detector in a chemical analyzer. The same circuit can be used for a bolometer instead of a photoconductor. Photoconductors require narrow bandgap materials, such as HgCdTe, and pose a problem by incorporating such materials into silicon integrated circuits, so that infrared spectra (eg, 1-20 T
The bolometer is useful in detecting (m wavelength).

The detector circuits connected to the radiation sensing elements are preferably integrated on the same silicon substrate 302, but are not shown in FIGS. 6 and 7 for clarity. Similarly, the support circuits of other embodiments are not explicitly shown.

The lens system focuses the radiation from the scene to be detected onto an array of detectors 200 and each detector 20
0 operates (synchronously) as follows. The radiation constantly irradiates the photoconductors 202, 204, and thus, in particular, the photoconductor 2 which is replaced by a bolometer
For the embodiment with 02,204, there is no scene setting time that gives an upper limit on the frequency. However, control and timing 230 applies a constant bias of +1 volt to contact 312 and a bias switch between +1 volt and -1 volt to contact 314. See the timing diagram of FIG. The common contact 310 is connected to an inverting input of an operational amplifier (op-amp) 210 that is apparently grounded.
Thus, when a +1 volt bias is applied to contact 314, both photoconductors 202 and 204 have the same applied voltage, and current through photoconductor is applied and passed through feedback resistor 212 to the output of operational amplifier 210. , The operational amplifier is-
The 2VR ₂₁₂ / R _PH. Here, R _PH indicates a common resistance of the photoconductors 202 and 204. Conversely, when a -1 volt bias is applied to contact 314, photoconductor 2
02, 204 have the same magnitude but applied voltages of opposite polarity. In this way, the current from the two photoconductors is erased at the inverting input of operational amplifier 210, and no current flows through feedback resistor 212, and the operational amplifier output is V0, which is _zero .

The correlated double sampler 220 is an operational amplifier 2
Take ten outputs and subtract the opposite polarity output from the same polarity output during successive bias polarity switching intervals. The result is a dc offset independent of the scene and an ac signal proportional to the radiation of the incident scene. This electronic bias switching and correlated double sampling
Significantly attenuates low frequency noise such as mechanical chopping and correlated double sampling. Thus, the output of operational amplifier 210 is comparable to the output of the amplifier of FIG. 1 with a chopping input having a bias polarity switching frequency corresponding to the chopping frequency. That is, this bias switching achieves electronic chopping.

FIG. 5 shows a correlated double sampler 220 including an operational amplifier 222 having a clamp switch 224, an input switch 226, and a capacitor 228. Switches 224 and 226 may be MOSFET transistors. Control-timing block 230 may use a ring oscillator to provide timing signals for sampling and clamping by bias polarity switching and correlated double sampler 220. The output of correlated double sampler 220 is half the bias switching frequency and is an analog value representing the sum of the dc offset due to the bias current through resistors 202 and 204 and the fluctuating signal due to fluctuating input radiation. Especially,
The correlated double sampler operates as follows. First, while the photoconductors 202 and 204 have opposite polarity biases, the switches 224 and 226 are closed, thereby charging the capacitor 228 to V ₀ and setting the output of the operational amplifier to zero. Next, the photoconductors 202, 20
4 have the same polarity bias, switch 22
6 is closed so that the input to the capacitor is 2VR ₂₁₂ /
R _PH , thereby changing the input value to the inverting input of operational amplifier 222 to 2VR ₂₁₂ / R _PH −V ₀ ,
And an operational amplifier output _{A (2VR 212 / R PH -V} 0)
Change to Here, A is an amplification factor.

Since the current flowing through the photoconductor 214 does not change in magnitude and only in polarity, no scene setting time is required and the chopping frequency is limited only by the capacity of this structure.

Detector 200 uses equal resistance, equal optical responsivity for resistors 202 and 204, and equal magnitude bias voltages. However, switching the bias polarity also suppresses noise even if these assumptions are relaxed. Poor quality in the magnitude of the resistance, optical responsivity or bias impairs the net responsivity and offset criteria of the detector, but does not alter the noise performance.
The detector 200 can use a bolometer element instead of a photoconductor in the same solution.

The preferred embodiment of the four component picture element detector 200 has a dc offset at the output of the operational amplifier 210 due to the bias current. FIG. 9 schematically illustrates a preferred embodiment detector 500 of a four component resistive element avoiding dc offsets. In particular, the detector 500
It includes photoconductors 502, 504 receiving input radiation and photoconductors 506, 508 shielded from the input, and includes an operational amplifier 510 with a feedback resistor 512, a correlated double sampler 520, and a control-timing 530. Again, the detector 500 may be one picture element of a picture element array in a video device, ie a single detector, and the photoconductor may be replaced by a bolometer.

Photoconductors 502-504 may be formed as two parts of a single resistive film of amorphous silicon 606, and photoconductors 506-508 are shown in plan view in FIG. Another single resistive film 2 of amorphous silicon 607 located below film 606 so as to be shielded from input infrared radiation as shown in FIG.
It may be formed as one part. The metal contact 610 is
Metal contacts 6 parallel to metal contacts 610 on the edge of membrane 606
Divide the membrane 606 into two equal parts with 12,614. The metal contacts are made of aluminum. Contact 61
The portions of membrane 606 between 0,612 and them form photoconductor 502, and the portions of membrane 606 between contacts 610,614 and between them form photoconductor 504. Similarly, contact 611 divides membrane 607 into two equal parts, and photoconductor 506 contacts contact 611.
And a membrane between the contact 613 and the photoconductor 508.
Includes a film between contacts 611 and 615. Membrane 60
6,607 are 50 (lm) x 50 (lm) respectively, 2
00 (nm) thick, and the film 607 is
It is on the upper oxide layer 605. Film 606 also blocks input radiation and resides on insulating layer 604 formed of alumina. The resistance of each photoconductor 502-508 is equal, approximately 20 megohms in the dark.

FIG. 12 shows the bias voltages (V ₁ , V ₂ , V ₃ and V _{4 in} FIGS. 9 and 12) applied to the _four photoconductors. Photoconductor 50 receiving input radiation
Reference numeral 2,504 denotes a photoconductor 202,2 of the detector 200.
It has a relative bias switch similar to 04. That is, it switches between +1 volt and -1 volt at the "chopping" frequency for photoconductor 502 and is a constant -1 volt for photoconductor 504. The shielded photoconductors 506, 508 also
It has relative bias polarity switching synchronized with the photoconductors 502,504. That is, the photoconductor 5
08 switches between +1 volts and -1 volts, and the bias of photoconductor 506 is a constant +1 volt.
Held by bolts.

Detector 500 operates similarly to detector 200. That is, first, the bias of photoconductor 502 is +1 volt (which has the opposite polarity to the bias of photoconductor 504), and photoconductor 5
08 bias is -1 volt (this is photoconductor 5
(With a polarity opposite to the bias of 06). At that time, the currents in the two photoconductors 502, 504 receiving the input radiation have the same magnitude but opposite polarities and act as zero current in the feedback resistor 512. Similarly, two shielded photoconductors 50
The current in 6,508 also has the same magnitude, but opposite polarity, and acts as a zero current in feedback resistor 512. As a result, the output of operational amplifier 520 is zero.

Next, the case of the same polarity bias will be considered. The _{photoconductors} 502 and 504 have the same polarity bias (-1 volt) and provide a current value of -2 _V / R _502-504 to the feedback resistor 512. Photoconductors 506 and 508 have the same polarity bias (+1 volt)
Has, given a current value 2V / R _506-508, R _502-504 wherein is the resistance of each photoconductors 502 and 504, and R _{506-50 8} is photoconductors 506 and 508 that are each interrupted Resistance. Now, assuming that the photoconductors 502, 504 are not illuminated with input radiation, they have the same resistance as the _{blocked photoconductors 506, 508} , so that R _502-504 equals R _506-508 , The current to the feedback resistor 512 is zero. However, if the input radiation is photoconductors 502, 504
It strikes the, R _502-504 is smaller than R _{506- 508,} 4 two photoconductors net negative current proportional to the input radiation density is given to the feedback resistor 512.
In fact, if R is the common resistance of the dark photoconductor and I is a small (small) decrease in resistance due to input radiation, the current through the feedback resistance is 2V
I / R, and its output is proportional to the input radiation.

When the four photoconductors do not have the same dark resistance due to mismatch, positive and negative bias mismatch, or the elements having different optical responsiveness, the detector 500 The same low frequency noise suppression comparable to mechanical chopping can be obtained. 13 to 15 show the experimental results. FIG.
5 shows the noise spectrum obtained from the detector 500 with a 1 volt steady bias applied to all photoconductors, filtered with a 3 dB per octave, 300 Hz bandwidth low pass filter, and without correlated double sampling. Transient 1 / f low frequency noise appears at a frequency knee of about 100 Hz. FIG. 14 shows the noise spectrum after applying a steady bias of 1 volt to all the photoconductors, filtering with a low-pass filter of 300 dB bandwidth of 3 dB per octave, and performing correlated double sampling. Thus, this is the minimum noise due to Johnson noise, which would have been obtained if the scene was mechanically chopped. Finally, FIG. 15 shows the noise spectrum due to electronic chopping (bias switching between -1 volt and +1 volt for two photoconductors) as described. FIGS. 15 and 14 are substantially equivalent, indicating that another bias switch required for electronic chopping does not adversely affect the transient or Johnson noise components of the detector. This indicates that the bias is switched but the magnitude is not changed and the output is not changed.

Another preferred embodiment of a two-component picture element FIGS.
1 schematically illustrates a radiation detector of a preferred embodiment of a component resistive element. Detector 900 includes a photoconductor 902 receiving input radiation, a photoconductor 904 blocked from input radiation, an operational amplifier 910 with feedback resistor 912, a correlated double sampler 920, and a timing-bias control 930. Photoconductor 90
2, 904, as shown in the plan view of FIG. 18 and the longitudinal section of FIG. 19, are formed from two electrically isolated resistance films 1006, 1012 of amorphous silicon. Metal contacts 1014, 1016 provide electrical contacts to photoconductor 902 and metal contacts 1018, 102
0 provides an electrical contact for the photoconductor 904. The membranes 1006 and 1012 are each 50 (lm) × 50 (l
m) is 500 (nm) thick, and the film 1006 is provided over the oxide layer 1004 over the silicon substrate 1002. Also, the film 1012 is located on the alumina insulating layer 1010 that blocks all scenery radiation transmitted through the film 1012. The alumina film 1010 is made of another insulating oxide layer 100
8 above. The dark state resistance of each photoconductor 902, 904 is about 50 megohms. In addition, a bolometer can be used instead of the photoconductor.

FIG. 20 shows two photoconductors 902,
904 shows bias voltages V ₁ and V ₂ applied to 904. Both photoconductors are the photoconductors 202, 202 of the detector 200.
+ At the same “chopping” frequency similar to 204
It has a relative bias polarity switch between V and -V, but the two biases have a 180 degree phase difference.

The detector 900 operates as follows. First, consider the case where the bias of photoconductor 902 is + V volts and the bias of photoconductor 904 is -V volts. This configuration has a current V / R ₉₀₂ -V / R
₉₀₄ to the feedback element 912 where R ₉₀₂
And R ₉₀₄ are the resistances of the photoconductors ₉₀₂ and _904, respectively. If there is no input radiation onto the photoconductor 902, R ₉₀₂ is equal to R _904, a current feedback resistor 912 is zero. However, when radiation is irradiated to the photoconductor 902, the resistance of R ₉₀₂ decreases, flows net positive current through the feedback element 912. The current is proportional to the input radiation intensity. In fact, if R is the common resistance of a dark photoconductor and I is a small (small) resistance decrease due to landscape radiation, the current through the feedback resistance is IV
/ R and the op amp output is proportional (feedback resistance to R ratio).

Next, consider the case where the bias of the photoconductor 902 is -V volt and the bias of the photoconductor 904 is + V volt. This configuration has a current V /
It gives the R _{90 4} -V / R ₉₀₂ to feedback element 912. Also, when there is no input radiation on photoconductor 902, the current in the feedback element is equal to zero and the output of the operational amplifier is zero. Conversely, photoconductor 90
2, the feedback resistance current is −IV /
R, and the op amp output is proportional.

The correlated double sampler 920 is an operational amplifier 9
Ten outputs are received and the output between one bias feature is subtracted from the output between the other bias features. In this way,
The correlated double sampler 920 outputs a result proportional to 2IV / R, and greatly attenuates low frequency noise in a manner similar to mechanical chopping.

[0030]Preferred Embodiment of A / C Bonding FIG. 21 shows the connection of the amplifier 1204 through the capacitor 1202.
Dual sampler 1206 with controller 1208
(Or bolometer) 90 coupled to
2 shows a modified example of the detector 900 having the reference numeral 2904. this
Capacitive coupling is the DC offset between the feedback resistors in FIG.
And the gain of the amplifier 1204 can be increased. Figure
20 is again applied to the photoconductors 902 and 904, respectively.
Applied bias voltage V₁, V_TwoAre simultaneously positive and negative
Switch between (chopping frequency of about 1KHz
), And have the opposite polarity. Bahia
Voltage V₁And bias voltage V_TwoPhotoconductor 90 between
2,904 resistance R₉₀₂, R_{90 Four}And capacity 1202 in parallel
Depending on the combination, (V₁-V
_Two) R₉₀₄/ (R₉₀₂+ R₉₀₄) -V_TwoGenerated voltage
Let If R is a dark photoconductor 902, 904
And if I is R due to landscape radiation
₉₀₂And the magnitude of the voltage of the capacitor 1202
Is equal to ± IV / (2 + I). Where V is V₁, V
_TwoIs the size of The bias of the photoconductor 902 is
+ V, and the bias of the photoconductor 904 is -V.
At some point, the voltage of the capacitor 1202 is equal to + IV / (2 + I)
When the bias polarity is reversed,
Sex is also reversed to -IV / (2 + I). in this way,
When the radiation of the landscape hits the photoconductor 902, the capacity becomes 1
The voltage at 202 toggles between positive and negative, and
Double sampler 1206 outputs 2IV / (2 + I)
(Assuming that the amplification factor by the amplifier 1204 is 1). Reeling
Again, electronic chopping by bias switching
And low frequency noise reduction. Example described earlier
As in the case of dark resistance or bias size mismatch.
The net response of the detector and offset pedestal
Adversely affect, but given by electronic chopping
Noise reduction is not affected.

Preferred Embodiment of Active Feedback FIG. 22 shows matched bolometers (or photoconductors) 1302, 1304, operational amplifiers 1308, temperature insensitive resistors 1312, 1314, operational amplifiers 1318, temperature insensitive resistors 1322, 1324, 1326, operational amplifiers. A detector 1300 having a 1328 and a correlated double sampler 1330 is shown. The input bias switches between + V and -V at the electronic chopping frequency.

The bolometer resistor 1302 receives input radiation (or has a radiation absorber in thermal proximity) and is heated, while the bolometer resistor 1304 is radiation blocked. The bolometer resistors 1302, 1304 are located adjacently on the integrated circuit board and they are
20 is subjected to the same thermal input and environment except that it is radiatively heated. Therefore, due to the radiation, the output voltage of the operational amplifier 1308 becomes approximately −V (1 + I
-T) _R1302 / _R1304 , where I is a small increase in resistivity per temperature C and -T is a temperature increase due to incident radiation; _R1302 and _R1304 are non-heated resistors 130.
2,1304. Resistance 1302, 1304
It is to be understood that the non-radiative heating or cooling of can yield the same increase or decrease factor for both resistances, which can be eliminated.

The output of the operational amplifier 1318 is equal to ± V (1 + R ₁₃₁₂ / R ₁₃₁₄ ), where R ₁₃₁₂ and R ₁₃₁₄ are the resistances of the resistors 1312 and 1314. The operational amplifier 1328 includes the operational amplifier 1308 and the operational amplifier 13.
The outputs of 18 are summed and supplied to a correlated double sampler 1330. In particular, the output of the operational amplifier 1328 is

V ₁₃₂₈ = −V ₁₃₀₈ R ₁₃₂₆ / R ₁₃₂₂ −V ₁₃₁₈ R ₁₃₂₆ / R ₁₃₂₄ = ± V (R ₁₃₂₆ / R ₁₃₂₂ ) (R ₁₃₀₂ / R ₁₃₀₄ ) _IT + ± VR ₁₃₂₆ [R ₁₃₀₂ / R ₁₃₀₄ R _1322- (R ₁₃₁₄ + R ₁₃₁₂ ) / R ₁₃₁₄ R ₁₃₂₄ ] Here, the subscripts indicate the same reference numerals. One (or more) of the resistors 1314, 1312, 1322, and 1324 can be varied or removed and can be adjusted to eliminate the second term on the right side of the equation, so that the current passing through the resistor 1322 passes through the resistor 1324 It means equal to the current. For example, by a resistor 1324 having a resistance value set as follows,

R ₁₃₂₄ = (R ₁₃₁₄ + R ₁₃₁₂ ) R ₁₃₀₄ R ₁₃₂₂ / R
₁₃₀₂ R ₁₃₁₄ The output of operational amplifier 1328 is

V ₁₃₂₈ = ± V (R ₁₃₂₆ / R ₁₃₂₂ ) (R ₁₃₀₂ / R
₁₃₀₄ ) _IT and correlated double sampler 1330 subtracts the negative bias output from the positive bias output,

## EQU4 ## 2V ( _R1326 / _R1322 ) ( _R1302 / _R1304 ) _IT is obtained.

[0034] Of course, bolometer element 1304 can receive input radiation, and bolometer element 1302 can be a blocked element. The operational amplifier 130
8 together with bolometer elements 1302-1304 can be used to directly drive correlated double sampler 1330.

Preferred Embodiment of Detector Array FIGS. 23 and 24 show a gas sensor 1400 of the preferred embodiment in plan and longitudinal sectional views. In particular, the gas sensor 1400 includes a chamber 1402, an infrared radiation source 1404, and four narrow bandpass radiation filters 14.
11-1414 and four radiation detectors 1421-14
24. Detector 1421 is a single picture element detector made of hydrogenated amorphous silicon and having a similar structure to detector 900 and using a photoconductor or bolometer located near optical filter 1411. Similarly, each of the other detectors is located near the corresponding filter. The chamber 1402 prevents external light from impinging on the detectors 1421 to 1424, and the gas flows as indicated by the arrow to form the chamber 1402.
Has a hole so that the contents of (1) reflect the atmospheric gas component. Infrared radiation source 1404 may simply be a low wattage light source. Filters 1411 to 1414 are approximately 0.2
1 m is a multilayer interference bandpass filter with a bandwidth of lm. The resistance of hydrogenated amorphous silicon used for bolometers is reduced by about 3% per 1 ° C. at room temperature.

Gas sensor 1400 detects the presence of three gases. It is carbon dioxide, water and volatile organics (VOCs) such as: The filter 1411 has a pass band with a central wavelength of 4.26 lm, which corresponds to the absorption band of carbon dioxide. Filter 1412 has a passband with a center wavelength of 2.7 lm, which corresponds to the absorption band of water. The filter 1413 has a center wavelength of 3.2.
It has a lm passband, which corresponds to a CH stretch bond, so that various organics absorb the wavelengths around this. Finally, the filter 1414 has a center wavelength of 3.
It has a pass band of 6 lm, which is far from the absorption zone by typical atmospheric gases. Infrared radiation source 140
4 generates broadband infrared radiation, and detector 1421 receives radiation passing through the gas in chamber 1402 and filter 1411. When the carbon dioxide concentration changes in the chamber 1402, the radiation received by the detector 1421 changes and is detected as described above. Filter 1411 ensures that other gas fluctuations in chamber 1402 do not affect the radiation received by detector 1421.

Similarly, the detector 1422 is connected to the chamber 14
02 to detect changes in water vapor concentration within
23 detects a change in the VOC concentration. For example, source 14
Fluctuations not caused by a change in the gas concentration in the chamber 1402, such as fluctuations in the irradiation of the laser beam 04, are detected by the detector 1424.
Perform calibration for 3. This information is detected by detectors 1421 to 142
3 for output compensation.

Details of a preferred embodiment of the elements of the sensor 1400 are described in the following section, which illustrates the filter 1411
1414 includes a single package of detectors 1421-1424.

Preferred for Kanthal Infrared Radiation Source
Infrared radiation source 1 of the first preferred embodiment of the embodiment sensor 1400
404 is a filament of Kanthal Al alloy (72% iron, 22% chromium, 5.5% aluminum and 0.5% cobalt) wound in a coil to illuminate a wide area and placed in a converging reflector Has lines.
The wire has a diameter of 0.1 mm and is wound in a cylindrical coil of about 2.5 mm diameter and about 4 mm long. Kanthal alloy wire is heated in air as a native oxide form that prevents further oxidation. The resistivity of Kanthal alloys is almost independent of temperature, so that the operating temperature depends only on the applied voltage. Kanthal alloys also have an emissivity of 0.7 over tungsten, so it is a more effective infrared source.

FIG. 25 shows that the gas to be analyzed is located at the focal point of the spheroidal
Shown is a coil 1502 of Kanthal alloy covered with an infrared window 1506 that prevents contact with 502. The openings of the reflector 1504 and the window 1506 are 25 mm in diameter, with a 2 mm gap between them for air flow.
The reflector has a spread of 40 mm and converges most of the infrared light to a range of about 10 mm diameter 100 mm away,
The light flux changes by a maximum of 3% over that region. A reflector 1504 with a coil 1502 is
It provides uniform illumination to 1424 and avoids coil 1502 imaging on the detector, which leads to fixed pattern problems. The light flux from the coil 1502 located at the focal point of the parabolic reflector is scattered and only a small amount of infrared radiation reaches the detector. Of course, other converging reflector shapes can also be used, provided they do not create a uniform light flux over the detector and disperse the light.

The coil 1502 is about 500-9000K
(Approximately 250-6000C). Window 15
06 is formed from germanium or zinc selenide or other infrared transmitting material, and reflector 1502 is made from any infrared reflector. If the temperature is high, roughly MT
^The infrared radiation becomes larger according to ^{4, and} the sensitivity of the detectors 1411 to 1422 is adjusted by selecting the voltage.

The Kanthal alloy may simply be on a surface on another support structure, and other air oxidation limiting alloys such as Nichrome (nickel and chrome) can be used.

The infrared radiation source 1 of the second preferred embodiment of the positive temperature coefficient ceramic IR source sensor 1400
404 is a metal film 1611,1 as shown in FIG.
Including the parabola of the rotating ceramic disk 1602 with 612. Disk 1602 is formed from a positive temperature coefficient ceramic (PTC ceramic). These ceramics exhibit a significant non-linear increase in resistivity at fixed temperatures selected within the range of 500-600 K by adjusting the composition of the ceramic. FIG. 27 shows the resistivity as a function of temperature. Electrical conduction occurs through the ceramic due to the voltage applied between the metal film 1611 and the metal film 1612, and the entire disk 1602 uniformly resistively heats above this fixed temperature,
The increase in the specific resistance effectively limits the further rise in temperature and obtains a cooling effect over a wide range. Disc 1602 biased at this fixed temperature thus provides a stable infrared source that is relatively easy to control.

One problem solved by an infrared source is:
This is the amount of infrared energy generated by this source. One standard solution is to send a lot of energy into a small filament and make the filament extremely hot, thereby emitting a reasonable amount of radiation. The same effect is achieved by using a large surface area to emit at lower temperatures. The blackbody curve shifts further to the IR side, and this source is more effective in IR. More power in the source is emitted at the appropriate wavelength for chemical sensing.

The parabolic shape shown in the sectional view of FIG. 26 has a certain directivity for light emission from the inner surface 1611 by reflection.
That is, while giving the general directivity indicated by arrow IR, the shape of disk 1602 can be changed to increase the light emitting surface. The opening of the parabola is 15mm in diameter, infrared transmission window 1
An air flow is ensured by a distance of 2 mm from 606, and the sample gas is isolated. A second possibility is to use a flat source in the parabolic reflector. This allows the use of commonly manufactured pill shapes and also has the effect of amplifying the reflector, however, the surface of this source is smaller than the surface of the total reflector PTC source. Finally, the spherical internal light emitting surface 1611 provides some directivity towards the center of the sphere, as indicated by the Huygens wavefront configuration.

Another problem to be solved is to optimize the surface of the IR radiation source in the desired range. A preferred embodiment of this source is to coat it with a similar coating, such as a dark metal, metal oxide or black varnish to improve emissivity.

The heat capacity of such a device makes pulsing its source very difficult. This type of source is best used with a bolometer equipped with an electronic or mechanical chopper.

Preferred Embodiment of Inclined Leg Bolometer The photoconductor pixels of FIGS. 6, 7, 10, 11, 18 and 19 reside directly on the lower substrate and are substantially thermally isolated from the substrate. Absent. 28-31 show plan, cross-sectional, and perspective views of a preferred embodiment bolometer structure 1700 that suspends a bolometer on a substrate for thermal isolation. In particular, the infrared absorber 1702 includes thermal insulating support arms 1706, 170 parallel to the lower substrate 1710.
7 is thermally coupled to an amorphous silicon temperature dependent resistor 1704 that extends to form 7. The support arms 1706 and 1707 are provided with inclined legs 1712 and 171.
Aluminum pads 1714, 17
Touch 15 Bolometer 1700 is about 50 (lm)
x50 (lm) and support arm 170
6, 1707 has an absorber 1702 and a resistor 1704 suspended about 2 (lm) above the substrate 1710. The inclined legs 1712 and 1713 have a long hollow triangular wedge of about 4 (lm) shown in the perspective view of FIG. 1
A single amorphous silicon layer having a thickness of
Resistor 1704 and arm 1 are doped with phosphorus or boron to have a resistivity of ~ 200 ohm cm and have a silicon nitride ("nitride") coating.
706, 1707 and inclined legs 1712, 1713 are formed. FIG. 29 shows a cross section taken along the line bb of FIG. 28, and shows the inclined legs 1712 together with the perspective view of FIG. Inclined legs 17
12, 1713 have strong mechanical attachment strength to the pads 1714, 1715. FIG.
A line cross section shows the absorber 1702 on the support arms 1706, 1707 and the resistor 1704.

The ramped leg structure can be generally used as a mechanical support capable of withstanding large lateral forces from film stress or from a purely mechanical structure in a micromachine or micromechanical device.

The preferred embodiment 1700 operates as follows. Absorber 1702 receives incident infrared radiation (generally substrate 1).
710) and is therefore heated. This heats the resistor 1704 and reduces it. Thus, the voltage between pad 1714 and pad 1715 creates a large current, and the sampling circuit described above detects an increase in current. Similarly, as the incident radiation decreases, the absorber 1702 cools, the resistance increases, the current decreases, and the sampling circuit detects the decrease.

The absorber 1702 and the resistor 1704 have a thin film structure, and therefore have a small heat capacity per unit incident radiation range. This gives high sensitivity (increase in temperature per incident watt of radiation). Support arm 1706, 1707
Have a width of about 2-3 (lm) and a length of about 40 (lm), respectively, and provide thermal isolation of the absorber 1702 and resistor 1704 structures. When operating in a vacuum, the absorber 17
02 and resistor 1704 lose heat primarily from the absorber to the substrate due to thermal conditions along the support arm. If desired, the support arms 1706, 1707 can be further lengthened (to increase thermal resistance) by stretching the resistor 1704. Absorber 17
02 has a three-layer structure, that is, a 50-nm-thick silicon nitride layer below the resistor 1704, and a silicon nitride layer 14 below this nitride.
The bottom layer is a 25 nm thick titanium layer and a 25 nm thick nitride underneath the titanium layer. Titanium absorbs infrared radiation and nitride provides electrical isolation and passivation from resistor 1704.

To minimize the electrical resistance of the support arms 1706, 1707, a thin (10-20 nm thick) metal strip (2 lm wide) of aluminum, nickel, titanium or other suitable metal is placed on the support arm 1706. Disposed along the amorphous silicon-nitride ramp leg 1712 and along one side of the resistor 1704;
Provide a low resistance path to See FIG. 29 and FIG. Similar metal strips are disposed along the support arm 1707 from the pad 1715 on the inclined legs 1713 and along the opposite side of the resistor 1704, and these metal strips also represent heat sources for the support arms 1706 and 1707. doing. FIG. 32 extends along the two sides of resistor 1804 on support arms 1806 and 1807 and provides a pad to the pad with ramps 1812 and 1813 to provide an absorber 1802 that provides more thermal insulation than that of FIG. FIG. 9 shows a plan view of a bolometer with metal strips 1820, 1821 to be joined. Since the thin metal layer does not sufficiently cover the steps, it extends from the pads 1714, 1715 to the upper end of the ramp and to the support arm metal 1820, 182.
A thick metal link (made of aluminum) may be formed to cover the sloping legs to the outside of one end. For example,
See metal tab 2207 in FIG.

[0053] Preferred embodiment Figure 33 to 36 how to make low stress shows the steps of a preferred embodiment of how to make a tilt leg of the bolometer 1700. In particular, the substrate 1710
Aluminum contact pads 1714, 171 on top
Start with any desired circuit, such as a 5 and correlated double sampler circuit. Pads 1714, 1715 are laterally or vertically connected to such a circuit via an intervening body. Next, the sacrificial polyimide 2 on substrate 1900 and aluminum pads 1905 and other exposed circuits.
(Lm) Spin on thick layer 1910. The thickness of the polyimide is equal to the desired spacing of the suspended bolometer on the substrate. Next, a 25 (nm) nitride layer and 14 (nm)
A titanium absorber layer is deposited. Next, titanium and nitride are patterned by photo printing and etching to form an absorber 1702 on polyimide 1910. next,
As shown in FIGS. 33 and 34, the photoresist 1920 is spin-on and patterned by a wedge-shaped circular intermediary body 1925. These interposers are located at the corners of absorber 1702. Polyimide 1910 and photoresist 1920 are simultaneously etched in a low pressure oxygen reactive ion etcher. The polyimide surface is eroded and the photoresist wedge points are also side etched, shortened and narrowed, gradually exposing more of the top surface of the polyimide wedge points, see FIG. Lower aluminum pad 19
Etch the polyimide until 05 is exposed. Finally, a wedge point having an inclined wall is obtained. Through this,
It can be easily coated by chemical vapor deposition or sputtering or evaporation material. FIG. 36 is a perspective view of FIG. 36 showing a single interposition, and FIG.
See the plan view of FIG.

Next, a 50 (nm) second nitride layer (which electrically insulates titanium) is deposited,
The amorphous silicon layer plasma enhanced chemical vapor deposition using the place doping PF ₅ or BCl ₃ in (nm) (PEC
VD), and then a 20 (nm) nitride layer is formed. The set of three layers forms a tilted leg, a support arm and a temperature dependent resistor. The stack of nitride, titanium, nitride, polysilicon and the top nitride passivation layer is relaxed to a minimum differential stress and the structure of absorber 1702 and resistor 1704 is bent by different stresses between the layers. It is controlled not to be. In fact, the plasma-enhanced state of nitride deposition is 5 × 1 from a compressive stress of ² × 10 ⁹ dynes / cm ^2.
Adjusted to create a range of tensile stress of 0 ⁹ dynes / cm ² . Thus, a lower stress (eg, 1 ×
Use nitride (less than 10 ⁹ dynes / cm ² ), then sputter titanium, which is typically very thin but stretchable, re-deposit low stress intermediate nitride and deposit amorphous silicon Finally, an upper nitride having low stress and a thickness necessary for ensuring the flatness of the layered structure after excluding the polyimide is deposited. In addition, the full nitride coating prevents chemical and humidity erosion for long-term stabilization of the resistance.

Spinning the photoresist, patterning it to define temperature variation resistance, support arms and tilt legs, and anisotropically etching amorphous silicon and nitride with a patterned photoresist as an etch mask;
Form resistance, support arm and ramp leg. As a result, pads 1714 and 1715 remain. See FIG.

The photoresist is spun on and patterned to define a thin metal electrical conductor along the support arm and extending from the angled legs to the aluminum pads 1714, 1715. Next, a metal layer such as aluminum, Ni or Ti of 10-20 nm thickness is deposited,
The photoresist is lifted off to form a metal conductor. Next, the photoresist is spun on and patterned by photo printing to form aluminum pads 1714,
A metal link connecting 1715 to the upper end of the ramp is defined, then 1000 nm of aluminum is deposited and the photoresist is lifted off to form the link. Finally,
Exclude the polyimide in the oxygen plasma, leaving a completed bolometer detector suspended on the substrate.

Preferred Embodiment of Super Pixel Bolometer Array FIG. 39 shows that each bolometer is similar to the bolometer 1800 and has ramped legs connected to pads connected to metal buses 2051-2055, so that the 4x suspended bolometers 2011 to 2044
FIG. 4 is a plan view showing a preferred embodiment of four arrangements. Each bolometer has an absorber area of about 35 (lm) x 35 (lm) and a total area (including metal buses 2051 to 2055) of 50 (lm).
x63 (lm). Metal bus bars 2051-20
55 is connected in parallel to all bolometers 2011-2044 (lines 2051, 2053, 2055 form one detector connection and lines 2052, 2054 form another detector connection), Although forming a single detector (super-pixel), it does not have a single large suspension range with attendant mechanical problems. In fact, if one or more of the bolometers 2011-2044 fails, for example, due to a broken support arm, the remaining 15 bolometers will still function and provide sufficient detector performance. further,
The parallel arrangement of N smaller bolometers improves the signal-to-noise ratio with a coefficient of ON for a single bolometer.

In particular, at low modulation frequencies (chopping) where the input radiation is low, the sensitivity of a single bolometer is a direct function of the thermal resistance of the support arm and the radiation absorption range. To the modulation frequency f _c, the sensitivity of the bolometer tanh (1 / f
_c ) includes other factors proportional to RC), where R is the thermal resistance of the support arm and C is the heat capacity (thermal mass) of the suspended material including the absorber. Typical values are as follows. f _c is about 30 Hz, R is about 2 × 10 ⁷ deg-sec
/ joule-m, C is about 10 ^-9 joule / deg. Thus, due to the modulation, increasing the absorber range to increase sensitivity results in an offset reduction of the tanh factor due to an increase in thermal mass C. Furthermore, an increase in the thermal resistance R for increasing the sensitivity also results in an offset reduction of the tanh factor due to the increase in R. Thus, a parallel bolometer array is
Without changing the thermal mass or thermal resistance of the individual bolometers,
Increase the absorption range.

In another method, the bolometers in one row (column) in the array are connected in series and the rows (columns) are connected in parallel, or the bolometers in one column (row) are Connect in parallel and then connect the parallel columns (rows) in series. This has the advantage of a simple connection. For example, in FIG. 39, the left metal line 2051 and the right metal line 2055 are two connection lines for the bolometer radiation absorption resistance.

Spiral support arm Super picture element bolome
Preferred embodiments view of over data sequence 40 is a plan view of a preferred embodiment of the 10x10 array 2100 of approximate square of the bolometer, the bolometer, and suspended on a substrate by tilting legged annular supporting arms connected to the pad This pad is
Or 2115 or metal lines 2121 to 2125, bus 2101 ties lines 2111 to 2115 together, and bus 2102 ties lines 2121 to 2125 together. FIGS. 41 and 42 show details of the bolometer by enlarging the 2 × 2 sub-array of the array 2100.
Each bolometer has a suspended film 2132 (e.g., a nitride / amorphous silicon / nitride) absorber 2130 to about 1348 lm ² over the entire range of about 1920 lm ^2. Inclined legs 2134 are connected to annular support arms 2136, each annular support arm being about 50 (lm) long and about 4 (lm) long.
(Lm) width, the annular support arms 2136 each have a thin metal strip for electrical connection and provide similar thermal resistance as the support arms 1806, 1807 of the bolometer 1800. Top metal level (aluminum,
Nickel, titanium or similar metal, about 10 nm thick, 3
(Lm) width) is from the inclined leg 2134 to the annular support arm 21.
36 and extends to an annulus 2138 along the edges of four adjacent bolometer films 2132 to form electrodes 2140 along each of these four adjacent bolometer films and a junction 2144 that is part of the annulus 2138. See FIG. 41 and FIG. Membrane links 2142 connect to the corners of four adjacent bolometer membranes that are not connected to annulus 2138. This provides mechanical support to prevent bending of the membrane. Like the bolometers 1700 and 1800, the bolometer film 2132 is composed of nitride / amorphous silicon / nitride.

FIG. 42 shows the bottom-level metal lines 211 and 21.
Reference numeral 12 indicates that the four inclined corner legs of the figure are connected thereto, and that the central inclined leg of the figure is connected to the metal wire 2121.

The support arm 2136 extends slightly more than 3/4 of the way to the complete annulus at the plane of the membrane 2132. In order to increase the thermal resistivity to the lower substrate, the support arm 2136 can be made longer by using a spiral shape, and more than one full rotation at the plane of the membrane 2132 can be achieved.

It is preferable to use a stress relaxation super pixel bolometer arrangement.
In the bolometer manufacturing described with reference to FIGS. 37 and 38, the reduction of the stress is achieved by the film of the super picture element 2100 generated at either the center or the periphery of the array as shown in the longitudinal sectional views of FIGS. Contact to substrate (loss of thermal insulation)
Requires process control to avoid bending of the suspended membrane that can cause FIG. 45 shows the super picture element 2170 of the preferred embodiment of the stress relaxation, which is the peripheral dummy picture element 2170.
171, and uses a deposition state centered on the parameter values giving a slightly upwardly curved membrane. The peripheral dummy picture element 2171 may be in contact with the substrate as shown in FIG. 45, but the active picture element 2173 keeps thermal insulation from the substrate. For a 10 × 10 active array, the super-pixel 2170 has a 12 × 12 pixel array and only the 10 × 10 sub-array pixels inside it are active. In this way, this peripheral dummy pixel allows a wide range of adhesion parameters to make a working superpixel, since the opportunity for downward bending is minimized and the upward bending does not damage the superpixel.

Furthermore, a saw-toothed edge may be added to the outer edge of the peripheral dummy picture element to reduce their thermal contact with the substrate. See FIG. 46 showing a 10 × 10 central active picture element 2173 and peripheral dummy picture elements 2171. A saw-toothed end 2175 is shown, showing larger teeth for clarity, but smaller teeth also provide additional thermal insulation.

Preferred Implementation of Hidden Support Arm Bolometer Array
施例 Figure 47 through Figure 50 show the fabrication steps of a preferred embodiment of a high fill factor of the bolometer array having a support arm at the bottom of essentially suspended absorber and resistance. This method allows for a minimum spacing between adjacent bolometers and is applicable when the bolometer array is used for imaging or high resolution spectrometer purposes, and where each bolometer is an individually sensed picture element. Of course, in this bolometer arrangement with a high filling rate, the pads 2201 in the row are both shown in FIGS.
It can also be used as a super picture element connected in the same way as 0 and used in chemical sensors. The individual bolometers shown in the plan view of FIG. 48 are square, but may be other tile shapes, such as rectangular and hexagonal. Bolometer is 5
An arbitrary size such as 0 (Tm) × 50 (Tm), the distance between adjacent bolometers may be as small as 1 (Tm) width, and the support material used during fabrication may be plasma-removable. In fact, the spacing between adjacent bolometers is less than or equal to the width of the support arm.

A preferred embodiment of the manufacturing method includes the steps and materials previously described with respect to FIGS. 33-36, and the process is as follows. (1) First polyimide layer 2203 (about 1 lm thickness)
Is deposited on a substrate with circuits already formed and with bolometer support arms connected to metal landing pads 2201 formed thereon. Landing pad 22
01 is provided with an interval according to a desired picture element size. Landing pad 2 through first polyimide layer 2203
Intermediates 201 are formed (using wedge photoresist and oxygen plasma etching of polyimide as previously described with respect to FIGS. 33-36). See FIG. 47 which shows a plan view of the left part and a corresponding sectional view of the right part.

(2) The support arm material and the electrically conductive material (for example, the same or different from amorphous silicon and metal) extending to the landing pad 2201 under the interposition body
A layer of This layer is patterned and etched by photographic printing to form a support arm. The support arm material may be patterned and etched prior to deposition of the conductive material and subsequent patterning and etching. Thereby, 4Tm width of 200 to 400 nm
A thick support arm 2205 is formed. To ensure an electrical connection from the electrically conductive material to the landing pad 2201,
The support arm 2205 does not cover all the landing pads 2201, and metal foot contact tabs 2207 are formed by deposition and photolithography by patterning and etching.
See FIG. Alternatively, if the support arm material and the electrically conductive material are separately patterned and etched, the electrically conductive material connects directly to the landing pad 2201 (similar to aluminum deposited on the amorphous silicon support arm of FIG. 29). Do).

(3) The second polyimide layer 2213 (about 1
(lm thickness) on the support arm 2205 and the first polyimide layer 2203, and the second polyimide layer 2213 fills the intervening body in the first polyimide layer 2203 and has a flat surface. An absorber is formed on polyimide 2213 by deposition of a layer of nitride and titanium followed by photographic printing and etching as described above. The absorber is located in the central part of the bolometer, similar to the absorber 1892 of FIG. Absorbers and resistors occupy 80-90% of the bolometer range depending on the bolometer size.

(4) Support arm 2205 separated from landing pad 2201 through second polyimide layer 2213
Is formed up to the end of. See FIG. 48, which shows a plan view on the left and a cross-sectional view corresponding to the right. Again, wedge-shaped interposers can be used. Next, a layer of nitride and amorphous silicon, a resistive material, is deposited. A stack of nitride, titanium, nitride, amorphous silicon, and (final) top nitride forms bolometer film 2215. As described earlier in the low stress section, the nitride can be deposited in a low stress state, and the nitride thickness at the top is used to prevent bending of individual bolometers.

(5) Patterning and etching the film 2215 by photographic printing to form separate picture elements, and also piercing the bottom polyimide film 2215 in the second polyimide layer 2213, The end of the support arm 2205 is exposed. A contact metal 2217 is formed by photolithographic patterning, metal deposition, and resist stripping to make electrical connections from the resistive material to the support arm 2205 and extend along one side of the resistor of FIG. . Similarly, thick metal links may be formed to connect the thin metal 2217 between the inclined legs to the support arm 2205. See FIG.

(6) Deposit the top nitride layer, pattern to separate the picture elements and eliminate both polyimide layers to complete the suspended bolometer. See FIGS. 49 and 50, which are longitudinal sectional views from a right angle direction.

Preferred Embodiment of Substrate Reference Resistance FIGS. 18 and 19 show a photoconductor configuration of the detector 900 of FIG. 16, wherein the photoconductors 902-904 are essentially thermally coupled to the substrate and 90
4 is blocked from input radiation by the photoconductor 902. The bolometer configuration of the detector 900 is further complicated because the bolometer 902 needs to be suspended above the substrate for thermal isolation, and shutting off a similar suspended bolometer 904 is not as simple as a photoconductor. The bolometer detector 2300 of the preferred embodiment avoids the problem by using an unshielded reference resistor 904 located on the substrate and made of the same resistive material as the suspended bolometer, eg, amorphous silicon. Support arm 2306,2
307, and nitride / amorphous silicon /
Inclined legs 2312, 23 suspending nitride film 2304
See FIG. 51 which shows a plan view of No. 13. Here, the lower substrate has an absorber 2302 on the suspended film and an adjacent resistor consisting of a nitride / amorphous silicon / nitride 2334 film immediately above the substrate. Metal films 2320 and 2321
Reduces the electrical resistance along the support arms 2306, 2307 and makes end contact with the suspended amorphous silicon resistance of the membrane 2304, as well as the aluminum membrane 2340,2
341 is in end contact with the amorphous silicon resistance of film 2334.

An alternative embodiment of the reference resistor 904. The resistance is placed in the storage area below the detector. This offers the advantage that, in the picture element arrangement used for image detection, picture elements ideally have as little inactive space in between. Such a substrate reference resistor does not need to be shielded because it is thermally coupled to the substrate that acts as a heat accumulator. In fact, such a reference resistor 2334 compensates for variations in substrate temperature since the substrate temperature is equal to the bolometer temperature without input radiation. Thus, with a bolometer resistor and a substrate reference resistance of the same material and resistance (size), a change in substrate temperature will lead to and cancel the same change in the two resistance values.

For a super pixel array bolometer, the substrate reference resistance has a proportionally smaller resistance, and the lower resistance is provided by a shorter film 2334 or by extending the aluminum films 2340, 2341 in a finger-like manner. Or it can be achieved by a combination thereof. See FIG. 52 showing the fingers 2342, 2343. For a single pixel bolometer resistance of 20 megohms and a 10x10 parallel connected bolometer array forming a super pixel,
The resistance value of the substrate reference resistor is simply 200 kOhm to match the resistance value of one hundred bolometers in parallel in the super pixel. The resistance of the film can be adjusted by adjusting the doping level. Depending on the reading circuit,
A resistance in the range of 1 kiloohm to 500 megaohm is desirable.

A reference resistor 2334 with metal contacts 2340, 2341 and thermally coupled to the substrate can also be located directly below the suspended bolometer element 2304. This allows the largest pattern range to be used and applies to both super-picture elements and single elements consisting of one range or linear range. FIG. 55 illustrates an associated support arm 235 spaced directly above the suspension membrane 2350 and the reference resistance membrane 2355.
3 shows a cross-sectional view. The same insulating material 2352 used for electrical insulation of the absorber 2351 is
357 can be attached to the top surface of the membrane 2355,
Can be used. Although not required for all applications, 2
The two electrodes are combined to form a common electrode 2354, which can further optimize the mold range. Common electrode 2
A similar schematic illustrates implementing a voltage divider network with a suspension element 2358 connected to a low thermal reference resistor 2360 by 359.

FIGS. 53 and 54 show the stage of manufacture of the detector 2300 following the stage described with reference to FIGS. First, a polyimide layer is formed over the circuit and metal landing pads and reference resistance terminals. Next, the photoresist is patterned with openings for the sloped legs (again wedge-shaped) and the location of the substrate reference resistor. As described above, a plasma etch is performed to erode the photoresist, excluding the polyimide, exposing a portion of the metal landing pad and the resistor terminals. Next, nitride, amorphous silicon and nitride are deposited and patterned by photo printing, as shown in FIG. Next, ion mill through nitride to expose the amorphous silicon and deposit aluminum, remove the resist, and finally remove the polyimide as described above.

Preferred Embodiment of Internal Shaded Package FIGS. 56-58 show an infrared detector 2401 with an infrared blocking film (shadow) inside the infrared transmitting package lid 2410. FIG.
2A shows a plan and longitudinal sectional view of a preferred embodiment of a 2 × 2 array of vacuum packages 2400. Narrow bandpass filters 2411-2414 on lid 2410 are located over corresponding detectors 2401-2404 and apertures in shade 2406. As shown in FIGS. 57 and 58, the shadow 2406 is
All incident infrared radiation is blocked from the detector except for the passage of the corresponding overlapping filters. The purpose of the aperture is to limit the (vertical) axis light to the detector below it and to prevent light internally reflected within the package from hitting another detector. The inner shade (as opposed to the outer shade) is closer to the detector and thus limits light to the target detector. In fact, shade 24
The aperture at 06 essentially interpolates the size difference between the (small) active area of the detector and the (large) area of the optical filter, shown by the ray traces in FIGS. FIG. 57 shows that detector 2401 receives radiation incident on a cone having an aperture angle of 26 ° and 41 ° from the direction perpendicular to the horizontal direction of FIG. 56, and FIG.
Indicates an opening angle of 50 ° in the vertical direction. This angle will vary depending on the application. Also, the ray 24 in FIG.
Numeral 50 indicates a shadow 2406 that blocks the passage between the detector 2401 and the filter 2412, and a ray 245 in FIG.
1 shows a shadow 2406 that blocks the passage between the filter 2411 and the detector 2403.

Each detector 2401-2404 comprises a single bolometer or bolometer array and circuitry and is a silicon integrated circuit of about 1.5 mm square, and the corresponding aperture of the shade 2406 is about 2 mm × 2.5 mm. Adjacent detectors are approximately 5 mm or 10 mm apart. Lid 24
10 is about 9 mm × 17 mm, and the ceramic package base 2430 is about 10 mm × 25 mm × 3 mm thick. The ceramic package base 2430 is made of sintered aluminum oxide with a gold seal band (for lid attachment) on nickel. Detectors 2401 to 240
Reference numeral 4 denotes gold: tin (80%: 20%) soldered to the ceramic package base 2430. The coupling wires between the detector and the package lead frame and the leads are not shown generally, only the outer portions of the leads before separation are shown in FIG. The lid 2410 is infrared transparent and is formed of 0.5 mm thick silicon (or germanium) with a germanium (or other) anti-reflective coating. The shade 2406 is a layer of gold / nickel / chrome having a thickness of 0.5 (lm). Detectors 2401 to 24
04 is about 0.25 mm away from lid 2410. The filters 2411 to 2414 are about 4 mm × 7 mm × 0.2.
5 mm thick multilayer interference filters, attached to lid 2410 with epoxy adhesive along their perimeter.

Preferred Embodiments of Vacuum Package The detectors 2401-2404 employ bolometers with thermal isolation, and sufficient gas pressure on the detectors 2401-2404 provides them with a thermally conductive path. Limit sensitivity. In fact, the gas pressure in the gap between the lid 2410 and the ceramic package base 2430 is 2
00mTorr or less, preferably 50-100mTo
rr should be maintained. Gold: Tin eutectic with lid 2410
Is attached to the ceramic package base 2430, and the detectors 2401-2404 are attached to the package base. The use of gold: tin instead of epoxy for attachment avoids exhaust gases from the organic epoxy entering the void. Gold / nickel / chrome shade 2
406 is formed by gold deposition avoiding the gas trap. Titanium / palladium / gold metal systems can also be used.
Chromium provides adhesion to the silicon lid 2410, and nickel provides a diffusion barrier between chromium and gold. Shadow 24
06 can be formed by raising gold / nickel / chromium deposited on a patterned photoresist that defines openings on the detector. Note that the gold / nickel / chrome extends around the lid and gold: tin connects the gold / nickel / chrome on the lid to the gold on the nickel seal band in the package base. Gold: Tin initially has a thickness of about 50-75 (lm), but is compressed during the seal. See the following description of the preferred embodiment of the sealing method.

A cold getter may be inserted into the void and activated. See FIGS. 59 and 60 showing getter 2470 maintained by wire bonds 2472 attached to the package floor. The getter may also be spot welded or soldered in place. Getter 2470 is comprised of zirconium-vanadium-iron or a similar gas sorbing material.

The cavity containing the detectors 2401-2404 has a volume of about 80 mm ³ . As a result of the experiment, about 2
Package 240 sealed at 00 mTorr initial pressure
0 maintained the cavity pressure below 300 mTorr after one year. That is, the package 2400 is 100 m in one year.
It indicates a pressure rise below Torr, and similar pressure rises can be applied to other initial pressures. Also, package 2400 is sealed at an initial pressure of 1 mTorr or less, and accelerated tests show that the pressure is maintained at 10 mTorr or less after one year. Thus, package 2400 has very low pressure applicability.

Package 2400 may be made from another material and maintain its vacuum performance. In particular, the lid may be a low-porous sintered ceramic or non-metallic (poly) crystalline material, or vented glass or VAR metal;
And since the gas emissions of all these materials are quite limited, the package base may be made of any of these same materials. Another method uses a convenient material, and a gas diffusion barrier (eg, silicon nitride) on the cavity surface
Is to apply. In fact, the package base has a gold coating, preferably on nickel, as a seal band and at the bottom of the cavity to connect to the gold: tin solder of the lid and detector respectively. Sealing Gold: Tin is replaced by other low outgas solder or low temperature sealing indium.

Another method of packaging and assembling is to solder lid 2410 to ceramic package base 2430 without vacuum and to provide a port to ceramic package base 2430 so that the cavity is evacuated after the lid is attached. . After evacuation, a low temperature indium solder seal (either molten or cold pressed) plugs the port. Alternatively, the port to the cavity may be a glass tube that is easily sealed after evacuation by melting.

Another form of vacuum package can be used for various micromachines or other structures, such as micromechanical resonators, and the lid need not be transparent. Gold: Use of a tin seal and evaporation or ion-plated outer gold layer on the lid eliminates outgassing seen with other lids and maintains a vacuum.

Preferred Embodiment of Vacuum Package Seal FIGS. 61 to 63 illustrate a vacuum package 2 including the following steps.
4 shows a preferred embodiment of the 400 sealing method. (1) Detectors 2401-2404 and getter 247
0 is suspended and the gold seal band on the lid 2410 is turned upside down, and gold: tin 2470 is placed around the lid (gold / nickel / chrome surface layer or equivalent) in a vacuum furnace. Gold: tin 2470 is tack-welded to the four corners along the (metal with). The furnace is evacuated to 0.001 mTorr. See FIG.

(2) The temperature of the furnace is maintained at 2700 ° C. for 24 hours to bake, and exhaust gas which may enter the cavity after vacuum sealing is removed. Gold: tin 2480 has a melting point of 2800 ° C
And is thus held in place on lid 2410.

(3) At the end of baking, the temperature is set to 310
Raise to ~ 3200 ° C and hold for about 6-7 minutes.
This will melt the gold: tin 2480 and further promote outgassing, but will increase the melting point without the gold dissolving in the gold / tin from gold / nickel / chromium. Lid 2 at the bottom of the package base, not in the opposite direction
Having the 410 prevents the molten gold: tin 2480 from falling off the lid 2410. See FIG.

(4) Lid 241 provided with molten gold: tin 2480 to form a seal by reflow for 2 to 4 minutes
The package base 2430 is moved down to 0. FIG.
reference. Gold: tin 2480 has an initial thickness of about 50-75 (lm) and compensates for flatness defects in the lid and / or package base. Next, the temperature is rapidly lowered to room temperature.

By baking, further activation of the getter is obtained. Getter 2400 chemically reacts with the surface adsorbed gas to become non-volatile, and thermal activation carries unreacted getter material to the surface, where it eventually reacts with the adsorbed gas after lid sealing.

An alternative is to use package base 243
0, but with gold: tin 2480 on the package base 2430. Baking times and temperatures can vary between 12 and 36 hours. Also, getter 2470 is electrically active, which allows for more complete activation,
Thus, a shorter bake is possible due to the larger getter capacity. Other materials can also be used, provided that the outer layer does not emit gas. Thus, sputtered gold absorbing argon (sputter factor) does not maintain a vacuum, but evaporated gold maintains a vacuum.

The characteristics of the chemical or physical state of a spectrometer system can be established by measuring infrared absorption or emission from the system over the entire wavelength range with a spectrometer. FIG. 64 is a plan view of a preferred embodiment of a spectrometer 2500 including a detector integrated circuit 2501, wherein the detector integrated circuit 2501 has 128 adjacent 2 × 1 in a package base 2530.
A gradation interference filter 2511 is provided below the linear array 2503 of the 0 super picture element bolometer and the infrared transmission cover 2510. Filter 2511 is a rectangular, bandpass filter with a center wavelength that varies linearly along the long side direction, the long side direction also being the longitudinal direction of the linear array of bolometers. The center wavelength varies by a factor of about 2 over the length of the linear array 2503. As described above, the wavelength band corresponding to the bolometer is a linear array 2503.
Along the longitudinal direction, which provides spectral separation. Of course, somewhat collimated input radiation limits crosstalk and improves resolution, but the closeness of pixels and the continuity of filters precludes the use of shadows.

By simply combining multiple bolometer arrays, a wider range of wavelengths can be analyzed. FIG.
Shows two contiguous sequences, with sequence 2551 being 2.0-4.0.
The array 2552 is below the filter 2562 having a center wavelength range of 3.5-7.0 (lm), and the array 2553 is below the filter 2561 having a center wavelength range of (lm). The array 2554 is below the filter 2564 having a center wavelength range of 10.0 to 20.0 (lm) and the array 2554 is below the filter 2564 having a center wavelength range of 0.0 (lm). Thus, the set of four arrays covers the range of 2.0 to 20.0 (lm) with slight overlap between the arrays, and the central wavelength range of a single filter does not exceed the ratio of two. The four arrangements together divide the spectrum approximately into 400 intervals, so that signal processing allows the spectrometer to
% Resolution.

FIGS. 66 and 67 are a plan view and a longitudinal sectional view of the bolometer range of the spectrum meter 2500 of the preferred embodiment. Each picture element is about 50 (lm) square, and the linear array is 12.8 mm long and 0.5 mm wide. Each super picture element has a value of 1 as shown in columns 2601 and 602 of FIG.
0 pixels are in two columns, the reading bus connects to the support between the two columns, and the adjacent super pixel is column 2
A bias voltage source is shared to connect to the support between 602 and 2603. The previously described electronic chopping device and substrate reference resistor are applicable, and the circuit can be placed in parallel in this linear array.

The gradation interference filter 2511 is made of multilayer dielectrics having different dielectric constants. The center wavelength of the pass band depends on the thickness of the layer, and the change of the center wavelength of the pass band comes from the change of the device thickness. Such filters are made by step-wise thickness growth of a dielectric layer, the number of layers determining the bandwidth of the pass band (eg, 5-10% of the center wavelength).

Automatic Calibration FIG. 68 schematically illustrates an automatic calibration circuit 2700 for the sensor 1400. Circuit 2700 compensates for lamp 1404 output changes and swings without using recalibration involving a standard gas sample. In particular, the detectors 1421 to 1421
One of the outputs 1423 is the "signal detector" output of FIG. 68 and the output of the detector 1424 is the "reference detector" output of FIG. Thus, three circuits 2700
Is used. One for each gas detector, and all three circuits use the same reference detector. Circuit 2
700 operates as follows. The output of the signal detector 2702 and the output of the reference detector 2704 are
It provides two inputs of zero, and thus the output of amplifier 2710 represents the amount of measured infrared light absorbed by the gas. This is all necessary if the infrared source 1404 was stable. However, when source 1404 swings, second differential amplifier 2712 causes reference detector 2704
Is compared with the calibration voltage 2706. Note that the calibration voltage 2706 may be made equal to the output of the reference detector 2704 during sensor assembly and calibration. Thus, the output of amplifier 2712 corresponds to the change in intensity of source 1404, which drives automatic gain control circuit 2720 to multiply the output of amplifier 2710 by a factor to restore it to its magnitude during sensor assembly and calibration.

The differential amplifiers 2710 to 2712 can be comprised of general purpose operational amplifiers, and the automatic gain control circuit is implemented as a voltage controlled resistor in the feedback loop of the operational amplifier as connected in an inverting amplifier. Of course, other circuits can be used for the difference amplifier and automatic gain control functions. The automatic calibration circuit 2700 can also be used without electronic chopping, simply by
702 to 2704 are resistance voltage dividers as shown in FIG.

[0097] self-calibration Figure 69 is read performs continuous calibration of the source strength circuit 2800
Shows a preferred embodiment, and also compensates for the ambient temperature of a sensor, such as sensor 1400, having both a signal detector and a reference detector. In particular, resistors 2802-2804 are resistors 902-904 of FIG. 16 for the detector of the gas to be measured.
And resistors 2852 to 2854 correspond to resistors 902 to 904 for the reference detector. That is, the resistance 2
802 receives the narrow band input infrared radiation around the absorption line of the gas to be measured, and the resistor 2804 is blocked from this radiation. Resistor 2852 then receives the narrowband input infrared radiation away from the absorption line of the gas to be measured, and resistor 2854 is also isolated from this radiation. The resistors 2804, 2854 may also be the substrate thermal reference resistors described in FIG. The reading circuit 2800 operates as follows.

First, the input radiation is ignored. Next, a resistor 2802 having the same resistance value and the same resistance temperature coefficient
And resistor 2804 means that the current through feedback resistor 2806 is zero, and operational amplifier 281
An output of zero is zero even if the ambient temperature changes. Similarly,
The output of the operational amplifier 2860 is a resistor 2852 and a resistor 285
It is zero when 4 has the same resistance value and the same resistance temperature coefficient.

Next, the light hitting the resistors 2802 and 2852
Input radiation from a source (eg, infrared source 1404).
The output of the operational amplifiers 2810 and 2860 is
And the input radiation passing through each of the reference filters.
ing. Next, these two opera by divider 2870
The ratio of the pump output is simply representative of the signal, regardless of the brightness of the light source.
ing. More specifically, R is the resistance 2 at the calibration temperature.
802, 2804, 2852, 2854
If I represents the temperature coefficient of the resistance, the temperature change -T
Causes a change in the resistance value of IR-T. Ambient temperature change
T_AAnd the signal resistance 28 whose input radiation is further changing
02 -T_sAnd the temperature of the reference resistor 2852
To -T_RAssume that At that time, the operational amplifier 2810
IIR_F-T_SWhere I is the V volt via
Resistance 2802, 2804, 285 at calibration temperature
2,2854, and R_FIs the feedback
Resistance (not sensitive to temperature) of resistors 2806, 2856
It is a resistance value. Also -T_ANote that time is omitted
I want to be. Similarly, operational amplifier 2860 is an IIR_F-T
_RIs output. Finally, divider 2870 provides its inputs and outputs.
Force ratio-T_S/ -T_RIn the output buffer 2872
Go. Thus, if the emission of an infrared light source varies by a factor
Then, -T_SAnd -T_RAre both changed by the same factor.
And does not affect the specific output. And of the gas being measured
When the concentration changes, -T_SChanges, while −T _RIs relative
And the output ratio generates a desired detection signal.
You.

To provide an input to divider 2870,
Electronic chopping can be applied by using two circuits of the FIG. 16 type. The divider 2870 may be an operational amplifier having an analog multiplier in a feedback loop. If the resistors 2802, 2804, 2852, 285
If the calibration resistance values of 4 are not equal, this is resolved by adjusting the applied bias voltage (eg, voltage divider) to equalize the calibration current. Of course, all of the above have employed linear approximations that satisfy the expected small temperature changes.

The resistivity of the thermally compensated bolometer resistor depends on the ambient temperature and on its own temperature which depends on heating by input radiation. Compensation for changes in the ambient temperature (thermal compensation) can be achieved by three types of reference resistors. It is an opaque bolometer resistor (light blocking bolometer), an infrared light insensitive bolometer (bolometer excluding the absorber), and a thermally non-functional resistor (substrate reference resistance) consisting of bolometer resistance material (substrate reference resistance). In each case, the input radiation does not affect the reference resistance, which tracks the atmosphere / substrate temperature. Figure 70
_{Is, Vout = - (R B /} R R) shows a circuit 2900 for providing thermal compensation in V _B, wherein R _B is the resistance value of the bolometer resistor and R _R is the resistance of the reference resistor. In this way, if the ambient temperature changes -T _A, infrared radiation heating further the temperature of the bolometer resistance is changed by -T _I, and has a temperature resistance coefficient of the resistors I, whereby these linear approximation the change in resistance due to temperature change is the product of R _B and the coefficient (1 + I-T _a) product, and R _R and the coefficient of _{(1 + I-T I)} (1 + I-T a). Therefore, the coefficients (1 + I-T _A ) and Vout only change by a factor (1 + I-T _I ) and affect the incoming infrared radiation.

A problem when sensing more gases with a sensor having multiple detectors, such as a dual detector sensor 1400 for increased sensitivity, is that the various gases have different absorption powers in their selective absorption band. That is. Another problem arises because different gases require different concentration detection levels. For example, if both CO and CO ₂ are to be detected, the C absorption in the 4.74 micron band is less than the absorption of CO at the wavelength of 4.74 microns.
O ₂ absorbs more strongly but is highly toxic
But it suggests that sensors that should have a greater sensitivity to CO than CO _2. However, the sensor is contrary to where desirable, sensitive to CO ₂ having a bolometric detector for each gas. From a manufacturing standpoint, it is desirable to create a versatile sensor platform that can make many products from the same material. The described vacuum package is versatile in gas sensor design because the optical filter that determines the gas to be sensed is installed after the fabrication of the detector package. this is,
It would be more beneficial to be able to change the sensitivity of the device for different chemistries within the framework of the sensor device.

The preferred embodiment solves both problems by using a simple multiple detector for a single gas to increase the sensitivity of the sensor to the gas. Multiplex detectors can be connected in parallel for large signals or treated as having separate circuits with separate gas sampling. FIG. 71 is a plan view of a single vacuum package with a 2 × 2 detector array and a single filter 2911 with a pass band at a wavelength of 4.74 microns for CO detection.
Filter 29 having a passband of 4.26 microns for detector 2901 and 2902, CO ₂ detection behind
13 behind the detector 2903 and the reference 3.
Filter 291 having a pass band of a wavelength of 6 microns
4 is provided with a detector 2904. Of course, filter 2911 may be two separate filters of the same wavelength. A 2x2 array can be used in sensors similar to sensor 1400. If the desired result is an increase in selectivity with an increase in sensitivity, multiple wavelengths can be used to sense the same type. Thus, the wavelength of the interference band with other substances can be selected, and the second band that does not interfere can be selected. The effect of the substance in question can be recovered from the interference band, and the signals from both bands are mixed. of course,
The same result can be achieved by selecting a second band as the band of interference and excluding that portion of the signal from the detector output.

Similarly, FIG. 72 shows a filter 29 for CO.
51 shows a 3x3 single package arrangement with four detectors behind, two detectors filter 2 for CO ₂
952 behind, and one detector H ₂ O, filter for volatile organic and reference respectively 2953-2
Behind each 955. Other arrays, such as 2x3 or 1x4, can be used in a similar manner. At the extreme, the spectrometer described herein is a group of detectors under specific filters and related parts of these filters that are tied to the associated absorption power and determined after the detector package is assembled. Can be formed.
It is important that the same physical result can be obtained by preferentially increasing the sensing range of one channel as opposed to another. This is not preferred as it directs the part to more specialized applications and adds cost.

Modifications The preferred embodiment has many modifications while retaining one or more of the features such as vacuum package multiple detectors, super picture elements, angled leg supports, internal shadows, tight support underpacking, and the like. . For example, various electronic chopping devices,
Packaging, pixel structure, filter settings and light source selection are made to form various sensor devices. The gas or liquid to be spectrally analyzed can be selected based on various criteria, and the bolometer sensitivity varies depending on the size and number of pixels.

If functional features remain, dimensions and materials can be varied. The bolometer structure includes other support devices such as four corner pillars, a support arm extending around the pixel, a common infrared absorbing and resistance changing material, a support arm that may be made of another material, and a bolometer membrane. be able to. The electronic chopping frequency should be above the 1 / f knee frequency and one of the photoconductors
/ F knee depends on bandgap (maximum wavelength detectable) and temperature. For example, with a mercury cadmium telluride compound having a band gap of about 0.25 eV (corresponding to a wavelength of 5 lm), the 1 / f knee at room temperature is a few Hz, and thus the bias switching is at least a few Hz. A common current source of reversible polarity that can be read ac or dc can be chopped electronically by polarity reversal as in the preferred embodiment.

[Brief description of the drawings]

FIG. 1 shows a known bolometer system.

FIG. 2 shows a known bolometer system.

FIG. 3 shows a known bolometer system.

FIG. 4 is a schematic block diagram of a first preferred embodiment of an electrically chopped detector.

FIG. 5 is a schematic block diagram of a first preferred embodiment of an electrically chopped detector.

FIG. 6 is a plan view and a longitudinal sectional view of a picture element according to the first preferred embodiment;

FIG. 7 is a plan view and a longitudinal sectional view of a picture element according to the first preferred embodiment;

FIG. 8 is a timing chart.

FIG. 9 schematically shows a detector of the second preferred embodiment.

FIG. 10 is a plan view and a longitudinal sectional view of a picture element of a second preferred embodiment.

FIG. 11 is a plan view and a longitudinal sectional view of a picture element according to a second preferred embodiment.

FIG. 12 is a timing chart.

FIG. 13 is a diagram illustrating noise suppression.

FIG. 14 is a diagram showing noise suppression.

FIG. 15 is a diagram showing noise suppression.

FIG. 16 is a schematic block diagram of another preferred embodiment of an electrically chopped detector.

FIG. 17 is a schematic block diagram of another preferred embodiment of an electrically chopped detector.

FIG. 18 is a plan view and a longitudinal sectional view of a picture element according to another preferred embodiment.

FIG. 19 is a plan view and a longitudinal sectional view of a picture element according to another preferred embodiment.

FIG. 20 is a timing chart.

FIG. 21 is a view showing ac connection of picture element.

FIG. 22 is a diagram showing an alternative arrangement of picture element elements.

FIG. 23 is a diagram showing an application of the preferred embodiment to a gas sensor.

FIG. 24 is a diagram showing an application of the preferred embodiment to a gas sensor.

FIG. 25 schematically illustrates an infrared radiation source of a preferred embodiment.

FIG. 26 schematically illustrates an infrared radiation source of a preferred embodiment.

FIG. 27 schematically illustrates an infrared radiation source of a preferred embodiment.

FIG. 28 is a plan, longitudinal, and perspective view of the bolometer of the preferred embodiment.

FIG. 29 is a plan view, a longitudinal sectional view, and a perspective view of the bolometer of the preferred embodiment.

FIG. 30 is a plan view, a longitudinal sectional view, and a perspective view of the bolometer of the preferred embodiment.

FIG. 31 is a plan view, a longitudinal sectional view, and a perspective view of the bolometer of the preferred embodiment.

FIG. 32 is a plan view of another preferred embodiment bolometer.

FIG. 33 is a diagram showing steps of a preferred embodiment of the bolometer forming method.

FIG. 34 is a diagram showing steps of a preferred embodiment of the bolometer forming method.

FIG. 35 is a diagram showing steps of a preferred embodiment of the bolometer forming method.

FIG. 36 is a diagram showing steps of a preferred embodiment of the bolometer forming method.

FIG. 37 is a diagram showing steps of a preferred embodiment of the bolometer forming method.

FIG. 38 is a diagram showing steps of a preferred embodiment of the bolometer forming method.

FIG. 39 is a plan view of a picture element array according to the preferred embodiment.

FIG. 40 is a plan view of a picture element array according to a preferred embodiment.

FIG. 41 is a plan view of a picture element array according to a preferred embodiment.

FIG. 42 is a plan view of a picture element array according to a preferred embodiment.

FIG. 43 is a plan view of a picture element array according to a preferred embodiment.

FIG. 44 is a plan view of a picture element array according to the preferred embodiment.

FIG. 45 is a plan view of a picture element array according to the preferred embodiment.

FIG. 46 is a plan view of a picture element array according to the preferred embodiment.

FIG. 47 is a diagram showing a picture element arrangement according to a preferred embodiment.

FIG. 48 is a view showing a picture element arrangement according to a preferred embodiment;

FIG. 49 is a diagram showing a picture element arrangement according to a preferred embodiment;

FIG. 50 is a view showing a picture element arrangement according to a preferred embodiment;

FIG. 51 shows a preferred embodiment of a suspended bolometer with a substrate resistor.

FIG. 52 shows a preferred embodiment of a suspended bolometer with a substrate resistor.

FIG. 53 shows a preferred embodiment of a suspended bolometer having a substrate resistor.

FIG. 54 shows a preferred embodiment of a suspended bolometer with a substrate resistor.

FIG. 55 shows a preferred embodiment of a suspended bolometer with a substrate resistor.

FIG. 56 is a plan view and a longitudinal sectional view of the package bolometer detector of the preferred embodiment.

FIG. 57 is a plan view and a longitudinal sectional view of the package bolometer detector of the preferred embodiment.

FIG. 58 is a plan view and a longitudinal sectional view of the package bolometer detector of the preferred embodiment.

FIG. 59 is a plan view and a longitudinal sectional view of the package bolometer detector of the preferred embodiment.

FIG. 60 is a plan view and a longitudinal sectional view of the package bolometer detector of the preferred embodiment.

FIG. 61 is a plan view and a longitudinal sectional view of a package bolometer detector of a preferred embodiment.

FIG. 62 is a plan view and a longitudinal sectional view of the package bolometer detector of the preferred embodiment.

FIG. 63 is a plan view and a longitudinal sectional view of the package bolometer detector of the preferred embodiment.

FIG. 64 is a diagram showing a spectrum meter according to a preferred embodiment.

FIG. 65 is a diagram showing a spectrum meter according to a preferred embodiment.

FIG. 66 is a diagram showing an embodiment of a spectrum meter according to a preferred embodiment.

FIG. 67 is a diagram showing an embodiment of a spectrum meter according to a preferred embodiment.

FIG. 68 is a schematic diagram of a preferred embodiment of automatic calibration.

FIG. 69 is a schematic diagram of a preferred embodiment of manual calibration.

FIG. 70 is a schematic diagram of a preferred embodiment of thermal compensation.

FIG. 71 shows a preferred embodiment of an array with a duplicate detector.

FIG. 72 shows a preferred embodiment of an array with a duplicate detector.

[Explanation of symbols]

 Reference Signs List 200 detector 202, 204 photoconductor 212 feedback resistor 210 operational amplifier 220 correlated double sampler 230 timing and bias control circuit

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Mark Buoy. Wadsworth Wentworth Drive, Richardson, Texas, United States 536 (72) Inventor William El. McCardel Town Bluff, Plano, Texas, USA 3845 (72) Inventor Kirk Dee. Peterson 1332 Minter, Plano, Texas, USA (72) Inventor Roland W. Gucci Sedwick Drive, Dallas, Texas, USA 6936 (72) Robert E. Inventor. Terrill 2702, Devonshire, Carrollton, Texas, United States (72) Inventor Mikle El. McHugh 7755 Eagle Trail, Dallas, Texas, United States

Claims (30)

[Claims] (A) a first terminal having a first terminal connected to an output circuit, the first terminal having a resistivity depending on a received radiation intensity;
(B) a second element having a first terminal connected to the output circuit and having a resistivity depending on the intensity of the received radiation; and (c) the first and second elements. And d. A first and a second voltage supply device having the same and opposite switching relative polarities respectively connected to the first and second voltage supply devices; and (d) the output circuit is a correlated double sampler synchronized with the switching polarity. Including a radiation detector. (A) third and fourth elements connected to the output circuit having a resistivity independent of received radiation; and (b) connected to the third and fourth elements, respectively. A third and a fourth voltage supply device, wherein the third voltage supply device has a polarity opposite to that of the first voltage supply device, and the fourth voltage supply device is the second voltage supply device. 3. The detector of claim 1, further comprising: the third and fourth elements having opposite polarities. 3. A first terminal having a first terminal connected to an output circuit, the first terminal having a resistivity depending on a received radiation intensity.
(B) a second element having a first terminal connected to the output circuit and having a resistivity independent of received radiation intensity; and (c) the first and second elements. And a first and a second voltage supply device having an opposite polarity and a relative polarity switching between positive and negative, respectively, and (d) the output circuit is provided with a correlation circuit synchronized with the switching polarity. Includes heavy sampler, radiation detector. 4. An operational amplifier having an input resistance and a feedback resistance, wherein the input resistance is connected to an input voltage supply device that switches polarity at a first frequency.
One of the input resistor and the feedback resistor having a resistivity dependent on the received radiation intensity; and (b) a correlator coupled to the output of the operational amplifier, synchronized with the switching polarity. A heavy sampler; and a radiation detector comprising: 5. A radiation source, and (b) a plurality of radiation detectors, each of said detectors remote from said source and receiving radiation from said source. A detector; and (c) a plurality of passband filters having different passband center wavelengths from each other, each of said filters being located between said source and a corresponding one of said detectors. And a plurality of the passband filters. 6. A radiation source comprising: (a) a radiation source; (b) a radiation detector remote from said source and receiving radiation from said source; (c) said radiation source comprising an air oxidation limited launch surface; Sensor, including radiation transmission window. 7. A radiation source, comprising: (b) a radiation detector remote from said source and receiving radiation from said source; and (c) said radiation source having a positive temperature between the electrodes. A sensor that includes a coefficient ceramic and a radiation transmission window. 8. A circuit board comprising: (a) a substrate including a circuit; and (b) a plurality of bolometers, each of said bolometers having a temperature-dependent resistance. (C) each of the bolometers comprises a plurality of arms supported on the substrate, the arms including conductors connecting the bolometers to the circuit such that the bolometers are connected in parallel; 9. The bolometer is arranged in rows and columns. (B) the support arms connect to column conductors on the substrate.
9. The radiation detector of claim 8, wherein the column conductor is below the row of bolometers, and (c) adjacent ones of the support arms have a common connection to the column conductor. 10. The bolometer is coplanar and parallel to the surface of the substrate; and (b) each of the support arms has a portion extending parallel to an end of the bolometer and the bolometer. The radiation detector according to claim 9, further away from the radiation detector. 11. A substrate including a circuit, and (b) a bolometer suspended on the substrate, the bolometer having a temperature-dependent resistance value, wherein the bolometer is a resistive layer made of a first material. (C) a plurality of arms supporting the bolometer on the substrate, wherein the arms include conductors connecting the bolometer to the circuit; d) a resistor thermally coupled to the substrate, wherein the resistor is comprised of the first material and includes a second resistive layer connected to the circuit; . 12. The bolometer has a radiation absorber on a film, the film comprises a stack of silicon nitride, amorphous silicon and silicon nitride, and (b) the resistor is a silicon nitride. The radiation detector of claim 11, comprising: a stack of amorphous silicon and silicon nitride; (c) the resistor is between the bolometer and the substrate. 13. A plurality of bolometers, each of said bolometers suspended on a substrate, each of said bolometers having a temperature dependent resistance. (B) each of the bolometers comprises a plurality of support arms for supporting each of the bolometers on the substrate, wherein the support arms are provided on an annular or spiral shaped portion and on the substrate below the center of the annular or spiral. A bolometer array containing the connecting ramps. 14. (a) said bolometers are arranged in rows and columns; (b) adjacent ones of said bolometers connect to a common one of said portions in an annular or spiral shape; (D) each of the bolometers is approximately square and one of the support arms is connected at two diagonally opposing corners; (e) the annular or Each of the spiral shaped support arms includes a conductor between the substrate and the bolometer;
14. The bolometer arrangement of claim 13, wherein the conductor extends on the bolometer parallel to one end of the approximately square bolometer. 15. The bolometer arrangement of claim 14, wherein (a) each of the bolometers is connected to any adjacent bolometer at a corner not connected to the support arm. 16. A substrate including a circuit, (b) a bolometer suspended on the substrate and having a temperature-dependent resistance, and (c) a plurality of bolometers supporting the bolometer on the substrate. Arms, the arms including conductors connecting the bolometer to the circuit, each of the arms extending from the substrate with the contacts of the arm, the substrate defining a depressed contact area having a V-shaped notch. A radiation detector comprising: the plurality of arms; 17. (a) each of said arms has a hollow triangular wedge at said contact; (b) said bolometer is flat and parallel to the surface of said substrate; (c) each of said arms is 17. The radiation detector according to claim 16, wherein the radiation detector extends parallel to an end of the bolometer and is remote from the bolometer. 18. A substrate comprising a circuit, and (b) a plurality of bolometers, each of said bolometers suspended on said substrate, each of said bolometers having a temperature dependent resistance. A plurality of bolometers; and (c) each of the bolometers comprises a plurality of arms supporting the respective bolometers on the substrate, the arms being located between the bolometer and the substrate. A radiation detector, wherein the arm includes a conductor connecting the bolometer to the circuit. 19. The bolometer is coplanar and parallel to the surface of the substrate; (b) the bolometers are arranged in rows and columns; and (c) each of the support arms is an end of the bolometer. (D) the support arm connects to a column conductor on the substrate,
19. The radiation detector according to claim 18, wherein the column conductor is below the column of a bolometer. 20. (a) providing an integrated circuit associated with a package base in a vacuum furnace; and (b) a package in the furnace adjacent to, but spaced from, the package base. Providing the package lid having a sealant adjacent to the periphery of the lid; (c) reducing the pressure in the furnace to a degassing pressure; and (d) removing the package base, package lid, and sealant. Heating to a degassing temperature below the melting point of the sealant and degassing said package base, package lid and sealant at said degassing temperature and degassing pressure; and (e) melting said sealant and said package lid. Joining the package base with the sealant at the degassing pressure Step a, the vacuum integrated circuit package assembly method and a step of solidifying the sealant to form a (f) shielding package. 21. (a) the base is ceramic with a metal seal band; (b) the lid is silicon with a metal layer adjacent to the periphery of the lid; (c) the sealant is gold 21. The method of claim 20, wherein the method is tin. 22. (a) said degassing temperature is within about 10 ° C. of said melting point; and (b) said step (e).
21. The method of claim 20, wherein joining comprises lowering the base on the lid. 23. The method of claim 20, further comprising the step of: (a) activating a getter attached to said base.
The described method. 24. A package base comprising: (a) a package base with embedded leads; and (b) a package lid sealed to the package base, wherein the package lid forms a cavity between the lid and the base. And the cavity is 300 mTorr
A vacuum integrated circuit package, characterized in that the pressure is less than 100 mTorr per year. 25. The package of claim 24, wherein (a) said pressure is less than or equal to 10 mTorr and increases by less than or equal to 10 mTorr per year. 26. (a) the base is ceramic with a metal seal band; (b) the lid is infrared permeable with a metal layer adjacent to the base; and (c) the lid is 25. The package of claim 24, wherein the base is sealed to the base with gold: tin solder between a metal seal band and the metal layer. 27. (a) a body; (b) a lid on said body and forming a cavity therebetween; and (c) a plurality of radiation filters on said lid, each of said filters being: A plurality of radiation filters transmissive to radiation in a passband centered on one wavelength; and (d) a plurality of radiation detectors in the cavity, each radiation detector comprising: A plurality of radiation detectors adjacent to one of the filters; and (e) a radiation blocking material on the surface of the lid in the cavity, wherein the material is adjacent to each of the radiation detectors. A radiation sensor comprising: the radiation blocking material having an opening. 28. The sensor of claim 27, wherein (a) each of the radiation detectors includes a bolometer, and (b) the cavity has a vapor pressure of about 200 mTorr or less. 29. A radiation source; (b) a radiation sensor remote from said source; i) a body; ii) a lid on said body and forming a cavity therebetween; iii). A plurality of radiation filters on the lid, each of the filters being transparent to radiation in a passband centered on one wavelength, wherein at least one of the wavelengths of the filter is to be sensed; A plurality of radiation filters corresponding to a gas absorption band; and iv) a plurality of radiation detectors in the cavity, each radiation detector being adjacent to one of the filters. And v) a radiation blocking material on the surface of the lid in the cavity, the material comprising an opening adjacent each of the radiation detectors. Having a gas sensor. 30. The gas sensor according to claim 29, wherein: (a) each of the radiation detectors includes a bolometer; and (b) the cavity has a vapor pressure of less than about 200 mTorr.